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標題: | 血管內超音波/光聲影像系統及探頭之開發 Development of Intravascular Ultrasound/Photoacoustic Imaging System and Probe |
作者: | Bao-Yu Hsieh 謝寶育 |
指導教授: | 李百祺(Pai-Chi Li) |
關鍵字: | 動脈粥狀硬化斑塊,血管內超音波影像,血管內光聲影像,全光學式超音波/光聲影像探頭, atherosclerotic plaque,intravascular ultrasound (IVUS),intravascular photoacoustic (IVPA) imaging,all-optical US/PA imaging scanhead, |
出版年 : | 2012 |
學位: | 博士 |
摘要: | 血管內光聲影像可利用組織間吸收光譜之不同藉此分析血管內斑塊成份,而血管內超音波則可提供血管及斑塊之結構性影像,在此研究中,將此光聲影像技術結合血管內超音波使成一雙模式血管內超音波/光聲影像系統,可利用光聲影像鑑別組織成份及高解析度超音波影像觀察血管狹窄程度及斑塊結構來診斷出心血管疾病。在此論文研究中可分為血管內超音波/光聲影像系統開發及整合型探頭開發兩部份。在系統開發上,為提升影像成像速度,藉由整合商用血管內超音波影像系統及高速雷射發展出即時血管內超音波/光聲影像系統,再加上錐狀末端光纖的使用來達到環型照光的效果,使得光聲影像擷取上不需轉動雷射激發方向以成像,以上技術之整合使得此系統幀率可達19fps,其超音波影像之橫向及軸向解析度分別為2.56°及62.4μm,而光聲影像之解析度分別為3.76°及 91.5μm。除了系統開發之外,在此研究中亦開發兩種以符合臨床血管內影像及高速成像為目的之新式微小型超音波/光聲整合探頭,來達到即時三維影像及降低雷射脈衝重覆率之需求。第一種探頭由環形超音波發射換能器、環形光源激發元件以及聚合物微環超音波接收共振器所組成,其中環形超音波發射換能器用於側向超音波的發射,並且使用光纖配合微錐狀鏡造成光轉折以做為光聲訊號的激發源,而在超音波/光聲訊號接收上利用一個光學式聚合物微環超音波接收共振器做訊號的接收以成像,以仿體影像驗證此探頭之可行性。另外,亦發展一新式全光學式超音波/光聲探頭,此探頭特性為無任何電子元件及傳統探頭之壓電材料,可降低拋棄式探頭成本,適用於血管內影像探頭,並具有發展成陣列探頭之優勢,在本研究中分別以兩種不同之光學設計來達到此一目的,首先,結合錐狀末端光纖及聚合物微環超音波接收共振器發展一全光學式超音波/光聲探頭,透過此設計在影像擷取上可利用單一發的雷射激發產生超音波及光聲訊號,並透過分頻影像處理的方法將超音波及光聲訊號分離,以增加此二訊號之對比度;另一項設計為解決訊號分離之問題,採用一雙色系統之設計,利用光學濾波器之分光特性,可藉由雷射波長之切換來達到超音波/光聲影像模式之切換,其影像可利用合成孔徑聚焦演算法以進一步提升解析度和對比度,橫向及軸向解析度可達2.52°和125μm,在本實驗中使用仿體影像驗證探頭之可行性。總體而言,本研究之重要貢獻為開發高幀率血管內超音波/光聲影像系統及探頭。此系統可有效擷取被影像物體及動物血管之超音波結構及光學吸收對比之影像資訊,以資為組織鑑別之依據;而新式全光學超音波/光聲影像探頭可提高血管內陣列超音波/光聲探頭之可行性。在未來工作中,可藉由結合環型激發及微型陣列探頭技術達到即時三維血管內超音波/光聲之成像,以期能達到心血管疾病診斷之目的。 Photoacoustic (PA) imaging combines good ultrasonic resolution with high optical contrast. In this thesis, integration of intravascular ultrasound (IVUS) and photoacoustic (IVPA) imaging was proposed for diagnosis of cardiovascular diseases. The hypothesis is that ultrasound (US) provide anatomical details of vessels, while the atherosclerotic and normal vessels can be differentiated by the photoacoustic (PA) techniques. In the first part of the thesis, we constructed a dual-modality imaging system for IVUS/IVPA imaging. A high-speed pulsed laser was used to increase the imaging frame rate for real-time IVUS/IVPA imaging. An optical fiber with an axicon-like distal tip was designed for omni-directional excitation, eliminating the need of fiber rotation. The imaging frame rate can reach 19 frames per second. Phantom and ex vivo experiments show that the lateral and axial resolution of US is 2.56° and 62.4μm at -6 dB, respectively. The PA resolution is 3.76° laterally and 91.5μm axially. In the second part, we developed two types of integrated imaging probes. One is an imaging scanhead with piezoelectric ring-shaped transmitter and the other is an all-optical IVUS/IVPA transducer. Both can be made sufficiently small for intravascular applications and a polymer microring was used for acoustic detection. Note that the all-optical design is suitable for one-time, disposable use. In the first all-optical design, the US signal is induced by impinging the laser energy on the substrate of the microring. A subband imaging method is subsequently applied to separate the PA signals from the US signals. In the second all-optical design, a dichroic filter is located at the outlet of the optical fiber to switch between US and PA imaging modes. The green laser pulse was absorbed by the red dichroic filter to induce an acoustic signal for US transmission, while the red laser light penetrated through the dichroic filter and illuminated the sample directly for PA imaging. The image resolution and the contrast can be further improved by applying the SAFT. The axial and lateral resolutions of this imaging system are 125μm and 2.52°, respectively. In summary, the thesis has realized effective IVUS/IVPA imaging methods for cardiovascular diseases diagnosis. The contributions include development of a dual-modality imaging system and various kinds of integrated imaging probes. Future works include high-frame-rate imaging techniques to achieve real-time 2D and 3D IVUS/IVPA imaging by integration of omni-directional excitation with a ring array transducer. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/63762 |
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顯示於系所單位: | 生醫電子與資訊學研究所 |
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